Ethernet Private Line (EPL) services may be offered today using Synchronous Optical Network (SONET) multiplexers, and many of the offered EPL services may be subrate services. A subrate service may be a service where a customer's user network interface (UNI) bandwidth is greater than a network bandwidth. For example, a customer may connect a local area network (LAN) Ethernet switch to a SONET multiplexer using a gigabit Ethernet interface which has a bandwidth of, e.g., “1000” Megabits per second (Mbps). However, the customer may subscribe for a network service of only, e.g., “150” Mbps. Such a scenario may be considered a subrate service because the customer's interface bandwidth (e.g., “1000” Mbps) exceeds a network service rate (e.g., “150” Mbps). Such a large discrepancy in speed between the customer interface and the network provider's service rate can result in traffic congestion during times of high traffic or traffic bursts.
Currently, the customer network interfaces (e.g., Ethernet switches) and the network provider interfaces (e.g., SONET multiplexers) used to provide EPL services do not support advanced traffic quality of service (QoS) mechanisms that prevent congestion during traffic bursts. Congestion may lead to dropped packets and retransmissions which may increase application latency and may lower the effective bandwidth of a link. Large traffic bursts that may exceed available bandwidth and lead to congestion may typically be intermittent and last for a short duration of time.
SONET multiplexers that may be used for EPL may support a Link Capacity Adjustment Scheme (LCAS). LCAS is a method that dynamically increases or decreases bandwidth of a network, and is specified in International Telecommunication Union (ITU) G.7042. LCAS may provide bandwidth on demand based primarily on time of day. The current features of LCAS work well if the customer knows exactly when the extra bandwidth may be required (e.g., over night to conduct a data backup operation). However, the timing of traffic bursts is unpredictable, and the current LCAS features fail to eliminate congestion during such traffic bursts.